Several Methods of Acid Etching SolutionAcid etching is the main chemical processing

Method in the PCB industry, which will produce a large amount of acid etching liquid waste. The acid etching liquid mainly contains copper, hydrochloric acid, sulfuric acid and oxidant. If it is not treated, it will cause waste of high value copper and serious environmental pollution. At present, there are sponge copper method, electrolysis method, extraction method, neutralization method, evaporative cooling crystallization method and other methods to treat acid etching solution, but there are various problems.

Sponge copper method is to add iron powder to react with acid and copper ions in acid etching waste liquid under acidic conditions. Iron is oxidized to divalent iron ions, and iron powder reacts with copper to obtain sponge copper and ferrous chloride solution after filtration by filter press. In this method, oxidant and acid are consumed with iron, hydrochloric acid and oxidant are not reused, and many chemicals need to be added to the production line. In this method, oxidant and acid are consumed with iron, hydrochloric acid and oxidant are not reused, and many chemicals need to be added to the production line.

The electrolysis method mainly uses current to conduct diaphragm electrolysis of acid etching waste liquid. Copper is electrolyzed at the cathode. A large amount of chlorine gas is generated at the anode, and the chlorine gas is dissolved and absorbed to the production line. The electrolytic anode is made of precious metal insoluble anode plate. The chlorine gas is dangerous, expensive and energy consuming, and the increment of waste liquid is also a problem.

The extraction method is to extract copper through extractants, and then electrolyze copper. The main problem is that a large amount of alkaline materials are needed to neutralize free acid. The extraction efficiency is also very low, the amount of waste liquid increases, and the electricity consumption of electrolysis is also large.

Neutralization method is to neutralize acid etching waste liquid with alkaline materials to make copper hydroxide, which is dried and dehydrated into copper oxide. The neutralized waste liquid cannot be reused and needs secondary treatment.

Treatment process of evaporative cooling crystallization method: acid etching solution → evaporative cooling crystallization → precipitated copper chloride for sale → precipitated etching solution is reused for etching line. This method requires a large amount of electric energy for evaporation and cooling, with high recovery value and good safety. This method has not been widely promoted in the industry. The main problems are high energy consumption, difficult ion separation, and high corrosivity of acid etching solution, The requirements for corrosion resistance of recycling equipment are very high.